1. Field of the Invention
The invention relates to a semiconductor integrated circuit (IC) device having a high breakdown voltage for controlling a high current, and to a method of manufacturing the semiconductor integrated circuit device. The semiconductor integrated circuit device according to the invention may be used as an IC for a switching power supply, an IC for driving the power system of an automobile, and an IC for driving a flat panel display. Specifically, the invention relates to a semiconductor integrated circuit device that incorporates a trench lateral power metal-oxide-semiconductor field-effect transistor (MOSFET) and one or more planar semiconductor devices, such as a planar MOSFET and a bipolar transistor, on a semiconductor substrate, and the method of manufacturing the semiconductor integrated circuit device.
2. Description of the Related Art
Recently, portable instruments have been widely used, and intelligent communication technologies have been developed. In association with these movements, power ICs that incorporate power MOSFETs have become very important devices. The conventional power IC combines a discrete power MOSFET and a control and drive circuit. In contrast, the new power IC developed recently integrates lateral power MOSFETs into a control circuit. It is required that the new power IC provide reductions in size, electric power consumption, and manufacturing costs thereof, and improve the reliability thereof. To meet these requirements, research and development of lateral power MOSFETs exhibiting a high breakdown voltage and being based on the CMOS process have been vigorously explored.
Usually, the planar power MOSFETs are manufactured using a process very similar to the process for manufacturing planar devices such as bipolar complementary metal-oxide semiconductors (BiCMOSs). Therefore, it is easy to obtain a one-chip power IC by forming a planar power MOSFET and the other planar semiconductor devices on a semiconductor substrate through the CMOS process. However, the integration density of the planar power MOSFET is not very high and improvement of the channel density of the planar power MOSFET, which reduces the on-resistance, is subject to certain limitations because the expanded drain region of the planar power MOSFET is formed along the substrate surface. Therefore, low efficiency of the power supply results and it becomes necessary to use a radiation fin or a large package with low thermal resistance to realize extremely low on-resistance for the power ICs.
Trench lateral power MOSFETs (TLPMs) have been proposed. For example, the present inventors have proposed TLPMs in “A High Density Low On-resistance, Trench Lateral Power MOSFET with a Trench Bottom Source Contact”, International Symposium on Power Semiconductor Devices and ICs (ISPD) Proceedings, pp. 143-146, 2001, and in U.S. Pat. No. 6,316,807B1. The trench lateral power MOSFETs facilitate high integration density. The trench lateral power MOSFETs are more advantageous than the planar power MOSFETs because the on-resistance of the trench lateral power MOSFETs is lower than that of the planar power MOSFETs.
FIG. 14 is a cross-sectional view of the active region of a conventional TLPM, which drives a current as a MOSFET. FIG. 15 is a cross-sectional view of the gate region of the conventional TLPM, which leads the gate electrode to the substrate surface.
FIGS. 14 and 15 illustrate a p-type semiconductor substrate 11, a p-type base region 12, an n-type source region 13, a p-type body region 14, an n-type expanded drain region 15, an n-type drain region 16, a trench 17, a gate oxide film 18, a gate electrode 19, a thick oxide film 20, an interlayer oxide film 21, a contact electrode 22, an oxide film 23, a metal source electrode 24, a metal drain electrode 25, and a metal gate electrode 26.
The TLPM having the structure described above is a discrete device. In other words, neither a power IC that integrates a TLPM and a BiCMOS device constituting a control circuit and a protection circuit on a semiconductor substrate, nor any method of manufacturing such a power IC has been realized yet. According to the prior art, a TLPM and an IC for a control circuit and a protection circuit are mounted on a wiring base plate and connected to one another via wires, for example.
The combined system, which combines a discrete TLPM and an IC for a control and protection circuit, poses problems such as an increase in cost caused by an increase in the number of constituent parts and elements and assembly steps, an increase in system size, and a reduction in reliability, as well as noise caused by the elongated wires for feeding gate signals.